Hydraulic system



Nov. 11, 1958 H. A. QMAUCH HYDRAULIC SYSTEM Filed Nov. 5, 1956 4,9: flfrae/ws' r United States Patent 2,859,451 HYDRAULIC SYSTEM Hans A. Mauch, Dayton, Ohio Application November 5, 1956, Serial No. 620,417

' 16 Claims. (Cl. 322) This invention relates to artificial limbs and more specifically to a hydraulic system particularly applicable to artificial legs to reproduce therein the muscle control pattern of a natural leg. While the invention system was developed primarily for solution of problems prevalent in above the knee prosthesis and will be particularly described with relation thereto, those versed in the art will readily recognize the application of the invention is not so limited.

The ultimate objective in the development of artificial legs has been to provide a control system which would automatically produce force characteristics on the leg components in the manner of the muscles of a natural leg. In this way the stride of the amputee using the artificial leg would specifically resemble the stride of the natural leg. The conventional artificial leg employed in above the knee prosthesis includes a thigh or socket section, a shank section, a foot, a knee joint between the shank and thigh sections, and possibly an ankle joint. The knee joint is generally provided by a single bolt about which the shank freely pivots relative the thigh, but polycentric knee joints have been employed. It is noted that either type of knee joint may be utilized in the practice of the invention.

In the natural leg the shank does not swing free about the knee joint. Extensor and flexor muscles connecting the thigh and the shank provide a dampening effect on the shank during the swing phase of each stride and a consistent leg motion control pattern thereby irrespective of the nature of the stride. Many devices of varied nature have been developed through the years in efforts to induce the force characteristics produced by the muscles of a natural leg in an artificial leg. These have proven to be only partial answers to the ultimate objective.

The present invention appears to be the first to provide a control system which faithfully reproduces natural leg control characteristics in an artificial leg. It specifically provides a novel hydraulic device inducing natural swing phase control of artificial legs. The device is connected between the thigh and the shank of the artificial leg to produce force characteristics about the knee joint which closely resemble the force characteristics of the natural leg as produced by its muscles during the same motions. The force characteristics are both negative and positive to relatively retard or assist the shank movements during swing phase action thereof. The invention device as employed in an artificial leg also includes means for convenient adjustment of these force characteristics, independently for bending and extending motions of the shank, to adapt the leg to the gait requirements of the amputee wearer.

An object of the invention is to provide hydraulic control means in an artificial leg to reproduce the control characteristics provided by the muscles of a natural leg therein.

A further object of the invention is to provide a hydraulic system of a highly advantageous and improved nature.

Another object of the invention is to provide an im proved hydraulic system capable of producing variable force characteristics of a precisely controllable nature within a single cycle of its operation, which is cyclically.

identical.

Another object of the invention is to provide an improved artificial leg including a hydraulic system therein providing force characteristics about its knee joint which closely resemble the force characteristics produced by the muscles in the natural leg during the same motions. and particularly during the swing-phase motions.

Another object of the invention is to provide an int-- proved artificial leg particularly applicable to above the:

knee amputees, having a control system therein to reproduce the motion pattern of a natural leg irrespective of.

the speed or length of stride in the use thereof.

A further object of the invention is to provide an im-- proved artificial leg including a control system therein: providing force characteristics about its knee joint which: closely resemble the force characteristics induced by the: muscles in a natural leg during similar motions and to additionally provide means for a convenient outside ad-- justment of the force characteristics, independently for bending and extending motions, in accordance with the gait requirements of the amputee employing the leg.

An additional object of the invention is to provide an improved swing-phase control system for artificial legs and the like.

Another object of the invention is to provide an improved hydraulic control possessing the advantageous: structural features, the inherent meritorious characteristics and the mode of operation described herein.

With the above and other objects in view, as will more fully appear in the specification, the invention intended to be protected by Letters Patent consists of the features of construction, the parts and combinations thereof and the mode of operation hereinafter described or illustrated in the accompanying drawings or their equivalents.

Referring to the drawings wherein is illustrated one, but obviously not necessarily the only form of embodiment and application of the invention;

Fig. 1 is a cross-sectional view of the hydraulic system provided by the invention; and

Fig. 2 shows an artificial leg employing the device'of Fig. 1.

The invention can be best described with reference to the drawings. Fig. 2 illustrates an artificial leg for above the knee amputees which consists of a thigh 1, a hollow shank 2 and a foot 3. A bolt 4, mounted in the depending extremity of thigh 1 so as to extend transversely of a recess 60 therein, pivotally connects the shank to the thigh and provides a knee joint thereby. As shown, the foot 3 is connected by a pivot pin 5 to the lower end of the shank and rubber shock absorbing pads 6 are interposed between the foot and the shank. However, the details and function of the ankle joint thus provided are not pertinent to the present invention and will not be a further described.

A hydraulic control system 7 respectively pivotally connects at one end to a pin 8 parallel to bolt 4 in thigh recess 60 and to hearing bracket 9 in shank 2 adjacent the lower forward wall therof at its other end. The nature of this system 7 as applied, causes it to contract when the artifical leg is bent at the knee joint and to expand Patented Nov. 11, 1958 when the leg is extended in a manner to be further detailed herein. It is noted that the pivot pin 8 may be located either ahead of or behind the knee joint 4, as desired, and the system 7 will function identically though in reverse With reference to Fig. 1 of the drawings, the system 7 includes a; cylinder 10 .closed at one end by a cap 11 whichhas a triangular plate 12 projecting from its outer face, diametrically thereof. This plate '12 is centrally apertured at 13 to receive a pivot pin14 therethrough to' connectit to the bearing bracket 9 in shank 2.

The other end of cylinder 10 has an annular flange 15 projecting radially inwardly to integrally connect to the outer extremity of a cylindrical housing 16 which concentrically nests within the'cylinder 10 in spaced relation thereto. The inner end 17 of the housing 16 is closed and provided with a central aperture 18 and a relief vent 19. The outer end 20 of housing 16 is open and slightly expanded in internal diameter. A thread 21 is cut into the inner wall of housing 16 immediately adjacent the expanded portion thereof.

An integrally connected cylindrical bearing 22 projects within the housing 16 from the inner end thereof, defining the aperture 18 therein. This bearing 22 is provided with a circumferential groove 23 seating a lip seal 24. The internal dimension of housing 16 adjacent its inner end 17 is conically reduced to provide a conical recess 25 about the inwardly projecting bearing 22.

A cylindrical control bushing 26, having its respective ends 27 and 28 externally tapered, seats in immediately nested relation within housing 16. The bushing 26 is radially expanded and threaded at 29 adjacent the outwardly positioned tapered end 28 for threaded engagement with the thread 21 in the inner wall of housing 16 as the bushing is inserted therein.

A cover screw 30 seats over and in the outer end of control bushing 26 to dispose its projecting knurled rim 31 about the outer end of cylinder 10. The screw 30 is centrally apertured at 36 and provides an externally threaded cylindrical body portion 32 threadedly engaging in housing 16 to thread 21 in the inner wall thereof. The inner face of body 32 is provided with a conical recess 33 identical with the recess 25 and axially aligned therewith. This conical recess 33 accommodates the outer tapered end 28 of bushing 26 in partially nested relation thereto to provide a conical gap therebetween. A 180 cut out 35 is circumferentially provided in the extremity of the tapered end 28 of the bushing 26, within the recess 33. As the cover screw 30 is engaged in housing 16 about the tapered end 28 of the bushing, a pin 34 fixed to body portion 32 projects radially inwardly therefrom into cut out 35. An operative connection is thus provided between the cover screw 30 and the control bushing 26 for conjoint or relative adjustment thereof with respect to the housing 16. The mounting of bushing 26 disposes the inner tapered end 27 in partially nested relation to the inner end 17 of the housing 16, within recess 25, providing a conical gap therebetween. The internal diameter of bushing 26 is such that the inner end seats about bearing 22 in concentric spaced relation thereto and the space therebetween is sealed by the lip seal 24 which is arranged to diverge to the inner wall of the bushing 26 in a direction inwardly thereof. A one-way check valve is thus provided at the inner end of the bushing 26 which will prevent fluid from escaping from the bushing but permits introduction of fluid therein. The aligned recess 33 in the opposed cap closure element 30 provides a central cylindrical bearing 55 defining the central aperture 36 therethrough. This bearing 55 has a circumferential groove, as bearing 22, seating a lip seal 37. The relationship of the cover 30 to the bushing 26 is such that the seal 37 diverges outwardly to the inner wallof the bushing and inwardly thereof to seal the outer end of the bushing in a manner to prevent escape ,of fiuid therefrom while providing for admission 'of fluid within the bushing 26 past the seal 37. Thus,

one-way valves are provided at either end of the control bushing.

A piston rod 38 extends through the aperture 36, in bearing relation to cover 30, axially of the bushing 26 and through bearing 22 into the cylinder 10 intermediate the inner end of the housing 16 and the end cap 11. The inner end of the piston rod 38 has a piston 39 fixed thereto which is contained and guided by the inner wall of the cylinder 10 while a smaller piston 40 is fixed about the rod 38 by snap rings 41 for movement Within the bushing 26, guided by the inner wall thereof. The outer end of the piston rod 38 projects outwardly of the cap cover 30 in the cylinder 10 which it seals and is provided with an eye 42 at its extremity for pivotal connection to the pin 8 in thigh 1 of the artificial leg as shown in Fig. 2 of the drawings.

The cylinder 10 is partially filled with hydraulic fluid 43 and substantially vertically disposed as shown to provide an air space 44 about the housing 16 at its upper or outer end. The housing 16 and bushing 26 are filled with the same fluid. The piston 39 has symmetrically disposed apertures 45 to allow fluid to pass the piston as it moves axially within the cylinder 10. However, the piston 40 is of solid construction.

The cylindrical body portion 32 of cover screw 30 is provided with aligned internal and external grooves seating 0 rings 46 to respectively provide a seal between the piston rod 38 and cover screw 30 and screwv 3t) and inner housing 16 at the outer end thereof. The.

assembly 7 is thus completely sealed.

The inside wall of the bushing 26 has two groups of axially and circumferentially spaced holes 47 and 48.

therein. The holes 47 arranged in circumferentially and axially spaced or staggered relation within the inner or lower half of the bushing 26are each connected by.

are each connected by a single downwardly extending channel 58 in the wall of the bushing 26 to the lower conical gap defined by the conically reduced interior .of

The channels 4-9 and 50 are each parallel to the central axis of the bushing 26 and cylinder 10 and are arrangedin alternating fashion within the wall of the control bushing around its circumference. The width of the respective conical caps to either end of the control bushing 26 is determined by the mutual position of the cover element 38 and control bushing 26 within the housing 16 and is effected in a manner and for purposes to be further detailed herein.

The hydraulic assembly 7 respectively connects to the bracket 9 in the shank 2 and to the pin 8 in the thigh 1 in the manner previously described. The operation of the hydraulic assembly in conjunction with the artificial leg is as follows. It will be first noted that in applying the control bushing 26 and the cover screw 30 within the housing 16 they are successively threadedly engaged to thread 21 within the housing 16 and by independent adjustment of the cover 38 relative the bushing 26 due to the pin cut out connection therebetween the upper and lower conical gaps of predetermined dimension are provided in a manner to be further detailed herein. Since the pin 8 lies behind the knee joint 4 in the artificial leg illustrated in Fig. 2 of the drawings, whenever the leg is bent, the piston rod 38 is pushed into the cylinder 10 and the pistons 39 and 40 move therewith. The hydraulic fluid in bushing 26 cannot escape through the lip seal 24 at the inner endof the bushing since the pressure of the piston 40 on the fluid maintains the seal effected thereby.

Therefore, only the holes 47 in the lower or inner half of the bushing 26 are available as avenues of escape for the hydraulic fluid. Thus, as the piston 40 moves downwardly from its normal position in the bushing 26 the fluid is forced through the openings 47 into the channels 49 and up and out into the upper conical gap between the cover screw and the tapered end 28 of the bushing. The fluid is then forced betweeii the cover element cylindrical body portion 32 and the inner wall of the bushing 26 at its outer end and past the oneway seal 37 to the other side of the piston. This completes the fluid cycle from the pressure side to the other side of the piston. The measure of fluid flow resistance produces a dampening effect on the piston rod 38 in the contracting movement thereof. This dampening effect is dependent on the width ofthe upper conical gap and the number and disposition of the holes 47 and channels 49 connected therewith. Due to staggered arrangement of the holes 47 in the inner wall of the control bushing 26, as the piston 40 moves to the inner end of the bushing 26, the number of holes 47 providing exits for the fluid being pressured by the piston 40 decreases. Thus, the fluid flow resistance increases gradually towards'the end of the stroke. This basically produces the dampening effect on the artificial leg which the muscles produce in a natural leg during the same motions. It will be apparent that by proper circumferential and axial spacing of the holes 47, the rate of increase of dampening effect can be varied over the piston stroke in order to precisely duplicate the force profile produced by the muscles in the natural leg. Similarly, the same sequence of events as described for the downward or contracting motion of the piston rod 38 basically occurs during the extending or upward motion of the piston 38. In the upward motion of the piston 38 on extending of the artificial leg as the piston 40 is moved upwardly within the control bushing 26 the holes 48 are progressively passed to reduce the number of outlets available for the hydraulic fluid being pressured by the piston 40 and accordingly a gradual increase in the flow resistance occurs and with a corresponding dampening eflect on the piston rod 38. As the piston 40 moves upwardly in the bushing 26 the fluid is forced out through the holes 48 into channels 50 and down into the lower gap about the inner end of the bushing and up through the seal 24 to the other side of the piston to complete the fluid cycle. The staggered or axially spaced arrangement of the holes 48 is diflerent from the arrangement of the holes 47 in this application since the force characteristics of the flexor and extensor muscles are also different from each other in the natural leg.

It should be noted here that while a piston 39 is employed on piston rod 38 within cylinder 10 in the illustrative embodiment of the invention, its function is prinsipally of a guiding nature. The invention obtains in absence of piston 39 on rod 38 with no appreciable difference in function.

Depending on the bodily configuration of the amputee, the control system in the artificial leg must be adapted in accordance with the gait requirements. vAlso, since the muscles in the natural leg provide a different measure of dampening, independently for bending and extending motions, means are provided by the invention for adjustment of the conical gaps to either end of the bushing 26 so that the dampening effects may be varied to suit the needs of the wearer of the leg. Referring to the details of the hydraulic assembly provided, as the cover element 30 is turned within the 180 range allowed by the cut out provided in the tapered end 28 of the control bushing, the control bushing will not participate in the movement of the cover. However, by screwing the cover screw 30 in housing 16 until its control pin 34 engages an end of cut out 35 in bushing 26, on further screwing both the cover and bushing will rotate to dispose the lower end of the bushing a predetermined extent within the housing 16 to provide a lower conical gap of desired dimension. The cover element 30 then may be adjusted within a range relative the upper tapered end 28 of the control bushing as permitted by cut out 35 to provide a desired upper conical gap. This adjustability of the cover 30 allows a simultaneous variation in the throttling effect on fluid flow through the upper exits of the channels '49 connecting within the bushing at the holes 47 in the inner surface thereof; Graphically speaking, therefore, each of these exits is throttled individually while the basic profile of the dampening characteristics produced in the system 7 is' maintained. Thus,the result of adjustment of cover 30 relative bushing 26 is to increase or decrease the dampen ing eifects on the piston 40 a measured degree for each point in the profile of movement thereof. Independent dampening adjustmentsare provided for both directions of movement of the piston rod thereby. The knurled rim 31 of the cover screw 30 afiordsconvenient accessible means outwardly of the shank for ready rotation of the screw 30 in either direction for the individual adjustment of the upper and lower conical control gaps provided in the hydraulic system.

In reference to the drawings, it will be noted that relief vent 19 affords the sole means of fluid communication between housing 16 and cylinder 10, connecting the lower gap adjacent the lip seal 24 with the fluid in cylinder 10. This allows the necessary fluid exchange between the housing and cylinder 10, either on operation of the cover screw 30 to adjust the conical gaps orin the event of temperature expansion or contraction of the fluid in the housing 16. The air space 44 in cylinder 10 allows the fluid 43 therein to rise and fall as the piston rod 38 is pushed into or pulled out of the system and also in the event of temperature expansion or contraction of the fluid therein.

It will be noted that the compression of air in space 44 during a contraction or compression stroke of the system will naturally produce a reaction to give the system an extension bias. Thus, in application to an artificial leg, the natural muscle-like controlled dampening of swing-phase movements of the leg is further enhanced by the natural-type forward bias given the leg by the system as the bending limit of the leg is reached.

Accordingly, the flexibility of the improved artificial leg as provided by the invention will be readily recognized. The limb may be applied in the ordinary manner and the amputee need merely adjust the screw 30 by engagement of the rim 31 through his pant leg until the dampening effects of the hydraulic system are adjusted to match the control eflects of the muscles of the natural leg. The closed fluid cycle as established and patterned by the control bushing 26, having the specific staggered arrangement of holes at either end connecting into the respective conical gaps to the other end of the bushing, insures that the basic profile of dampening characteristics as provided by the muscles of the natural leg will be constantly maintained in the artificial leg.

A hydraulic controlled artificial limb is provided which automatically reproduces in mechanical form the characteristic muscle response provided for similar motions in a natural limb. To all intents and purposes the artificial limb modified in accordance with the invention will function in the manner of a natural limb.

The invention has been described with considerable particularity relative artificial legs since it promotes such a marked improvement and advance in the art. However, those versed in the art should readily see the wide adaptability and range of application of the hydraulic system of the invention. The insured precisely controllable dampening eflfects provided and the ready adjustability of the rate and degree of these dampening eflects are of significant importance in the control field. This is recognized and defined herein.

From the above description it will be apparent that there is thus provided a device of the character described possessing the particular features of advantage before enumerated as desirable, but which obviously is susceptibieof modification in its form, proportions, detail construction and arrangement of parts without departing from the principle involved or sacrificing any of its advantages.

While. in order to comply with the statute the invention has been described in language more or less specific as to structural features, it is to be understood that the invention is not limitedto the specific features shown, but/that the means and construction herein disclosed comprises an illustrative, form of several modes of putting the invention into etfe'ct and the invention is therefore claimedin any of its forms or modifications within the legitimate and valid scope of the appended claims.

Having thus described my invention, I claim:

1. An artificialleg comprising a hollow shank, means for mounting said shank in pivotal relation to a thigh,

a hydraulic cylinder pivotally connected to said shank a hydraulic cylinder pivotally connected to said shankinternally. thereof and having means for connection of said cylinder in pivotal relation to the thigh, said connecting means being axially movable within said cylinder, control. means within said cylinder and operatively connected to said connecting means, automatically responsive to swing phase movements of said shank for imposing a dampening effect on said shank that varies in a, predetermined pattern as movement of the shank progresses through its operating cycle, and means. connected to said cylinder and to said control means for outside adjustment of said control, means and the varying darnpeningeifect imposed thereby to adapt said leg to the gait requirements of an. amputee.

3. An artificial leg comprising a hollow shank, means for mounting said shank in pivotal relation to a thigh, a hydraulic cylinder pivotally connected to said shank internally thereof and having means for connection of said cylinder in pivotal relation to the thigh, said connecting means being axially movable within said cylinder, control means within said cylinder and operatively connected to said connecting means, automatically responsive to swing phase movements of said shank for imposing a dampening effect on said shank that varies in 4 a predetermined pattern as movement of the shank progresses through its operating cycle, and means adjustably connected to said cylinder and to said control means for adjusting the degree of said dampening eif ect to adapt said leg to meet the gait requirements of an amputee.

4. An artificial leg including a socket, a shank pivotally related to said socket, control means connecting said shank and said socket, and means operatively con nected with said control means and responsive to swinging movement of said shank relative said socket to introduce positive andnegative force effects thereon which vary in apredetermined pattern in the cycle of movement of said shank in the manner of the muscles of a natural leg.

5. An artificial leg including a socket, a shank pivotally related to said socket, control means connecting said shank and said socket, means operatively connected in said control means and responsive to swinging movement of said shank relative said socket to introduce posifor outside adjustment of said force eflects, independently for opposite directions of movement of the shank, to,

adapt the leg to the gait of requirements of an amputee.

6. An artificial leg comprising a thigh, a shank, means connecting said thigh and said shank to produce a. dampening eiiect on said shank that varies in a predeten.

mined pattern as the movement of the shank progresses through the swing phase movement thereof and means.

operatively engaged to said connecting means for adjustment thereof to adapt the leg to the gait of an amputee while maintaining the predetermined pattern of the dampening eifect in a manner similar to the muscles of a natural leg.

7. An artificial leg comprising a thigh or socket sec tion, a shank section pivotally connected thereto about means providing a knee joint therebetween, means connecting said shank and said thigh to produce a dampening eifect on said shank that varies in a predetermined pat tern for the bending and extending motion of said shank,

and means in said connecting means for adjustment of.

the; control provided by said connecting means, independently for the bending and extending motion of said shank.

8. An artificial leg including a thigh or socket element, a shank pivotally connected to said element for swinging movement about a knee joint, extensible and contractable means connecting said shank to a point on said thigh adjacent the knee joint, said means including relatively reciprocable elements, dampening means op eratively connected with said relatively reciprocable, elements for imposing a dampening effect on said shank that varies in a predetermined pattern respectively on extension and contraction of said connecting means during swing phase movement of the shank, and a single.

control means connected to one of said relatively recipro-.

cable elements. operative to adjust the degree of said dampening of said shank independently for contraction and extension during swing phase movement of the leg.

9. A hydraulic control system comprisinga cylinder substantially filled with hydraulic fluid concentrically mounting a fluid-filled housing therein open to one end, a piston rod extending axially of said cylinder through and in bearing relation to the other end of said housing, a piston on said rod within said housing, and control means mounted within said housing to provide a closed fluid system therewith, said control means including means for progressively dampening the movements of said piston at selective intervals in the cycle thereof to.

produce varying force characteristics Within each cycle.

10. A hydraulic control system comprising a cylinder substantially filled with hydraulic fluid concentrically mounting a fluid-filled housing therein open to one end, a piston rod extending axially of said cylinder through and in bearing relation to the other end of said housing,

a piston on said rod within said housing, control means mounted within said housing to provide a closed fluid system therewith, said control means including means for progressively dampening the movements of said piston at selective intervals in the cycle thereof to produce varying force characteristics within each cycle, and said control means including an adjustable cap for said one end of said housing operable to adjust said control means to provide independent adjustment of said varying force characteristics for opposite directions of movement of saidpiston.

11. A hydraulic unit including a cylinder having hydraulic fluid therein, a pair of pistons operable in said cylinder having a rod connected therebetween and extending from said cylinder for reciprocation of said pistons, 21 control housing having hydraulic fluid therein Containing one of said pistons and having means mounted therein for progressively resisting the movement of said One piston on actuation thereof by movement of said rod, and means connected to said control means and to said cylinder for adjustment with and relative to said control means to selectively increase or decrease the progressive resistance to movement of said one piston.

12. A hydraulic unit comprising a cylinder containing hydraulic fluid, a piston therein having a piston rod connected thereto and extending from said cylinder, a fluid filled housing fixed in said cylinder about said rod and said piston, a control bushing in said housing about said piston having one-way seals at either end thereof to prevent escape of fluid therefrom but allow introduction of fluid within said bushing, axially spaced holes in the inner wall of said bushing to either end thereof, means connected in said housing providing gaps at either end of said bushing adjacent said seals, each of said holes at either end of the bushing being respectively connected into a gap at the other end of said bushing whereby on reciprocation of said rod, increased resistance to movement of said piston occurs as said rod approaches either extreme of its cycle, the fluid in said housing being moved from one side of said piston through said holes and through the gap with which they communicate and through the adjacent seal of the control bushing to the other side of said piston in a closed cycle.

13. A hydraulic unit comprising a cylinder, a piston therein having a piston rod connected thereto and extending from said cylinder, a housing fixed in said cylinder about said rod, a second piston fixed to said rod for reciprocation therewith in said housing, a cylindrical control bushing in said housing about the rod and said second piston having one-way seals at either end to prevent escape of fluid therefrom but allow introduction of fluid therein, holes circumferentially and axially spaced about the inner Wall of said housing, means providing gaps at either end of said housing in communication with the respective ends of said control bushing, each of said holes at either end being respectively connected into a gap at the other end of said housing whereby on reciprocation of said rod increased resistance to m vement of said second piston occurs as said rod approaches either extreme of said bushing, the fluid in said housing being moved by said piston through the holes in the wall of said bushing and into the gap with which they communicate and through the adjacent seal of the bushing to the other side of said second piston and a relief vent in said housing adjacent one of said gaps and communicating with the cylinder to provide means for fluid expansion or contraction.

14. An artificial leg including a thigh, a shank, a first housing pivotally connected to said shank, a second housing connected thereto, said housings having hydraulic fluid therein, a piston in one of said housings, said piston having a rod connected for reciprocation thereof, said rod being pivotally connected to said thigh, a control bushing in said one of said housings guiding the piston therein, means sealing said bushing against escape of fluid from the respective extremities, and staggered holes in the inner wall of said bushing connecting into channels in the walls thereof, providing the only outlets from the said bushing, and channeling means at either end of said bushing in communication with the sealed ends thereof and with said wall channels whereby on bending or contracting of the artifical leg the movement of said rod will result in a dampening of the movements of the piston in said one housing and correspondingly of the movements of said shank in a manner similar to the muscles of a natural leg.

15. An artificial leg comprising a thigh, a shank, a cylinder connected to said shank, a fluid-filled housing within one end of said cylinder, a first piston in said housing, a second piston in said cylinder, a piston rod connecting said pistons for reciprocation thereof, said rod being pivotally related to the thigh, a control means within said housing guiding said first piston and including means progressively dampening the movements of said first piston as it is displaced from a normal position, said control means having means connected therewith for varying the degree of the progressive dampening.

16. An artificial leg comprising a thigh, a shank, a cylinder, a housing mounted concentrically within said cylinder at one end and spaced from the inner wall thereof, said housing and said cylinder accommodating hydraulic fluid, a cover screw threadedly engaged in said housing at the outer end thereof, a piston rod extending through the cover screw and the inner end of said housing, in bearing relation thereto, and into said cylinder, a control bushing threadedly engaged in immediately nested relation to said housing between the cover screw and the inner end of said housing, one-way lip seals sealing said bushing at the respective ends thereof to prevent escape of fluid therefrom, the mounting of said bushing providing spaces in said housing adjacent thereto, said cylinder and said rod being pivotally connected to said shank and said thigh, said bushing having holes in the inner wall thereof providing the only outlets from said bushing and selectively communicating with one of said spaces, piston means fixed to said rod within said sealed bushing, said holes being so arranged that on bending or extension of the leg said rod will be pushed into or pulled out of said cylinder and the fluid in said bushing will be moved by the piston means therein against increasing flow resistance for imposing dampening characteristics on the shank during bending or extending motions similar to that provided by the muscles of the natural leg during similar motions.

References Cited in the file of this patent UNITED STATES PATENTS 984,377 Kilgour Feb. 14, 1911 1,494,135 Robison et al May 13, 1924 2,561,370 Henschke et a1. July 24, 1951 FOREIGN PATENTS 414,072 Italy June 27, 1946 

